The present invention is in the field of the machining of parts. More particularly, the present invention is directed to a light-weight, modular work-holding chassis, or “tombstone”, for mounting work pieces so that they may be machined. Applicant hereby claims priority of provisional patent appl. No. 60/508,025 filed Oct. 1, 2003.
The use of work-holding chassis for mounting work pieces which are carried from station to station in a) a horizontal machining center or b) a vertical machining center with an indexer or, c) in a transfer line, for performing various machining operations thereon is known in the industry. Indeed, the use of work-holding chassis is widely preferred due to the part density which can be achieved by fixturing parts to all sides of the chassis. Work-holding chassis permit the machining of parts from many directions, particularly if the chassis can be indexed (i.e., in a horizontal machining center or a vertical machining center with an indexer). The shape of the chassis is dictated by a number of factors: 1) the size of the workpiece, 2) the size of the machine, and 3) tool clearance issues within the machine. The more sides available, the more parts which can be fixtured at any one time.
While some work-holding chassis have manually operable clamping, health issues have helped drive the industry toward the use of hydraulic clamping. Elimination of manually operable clamping reduces incidents of worker fatigue and carpel tunnel syndrome. Hydraulic clamping is also preferred due to its consistency and ability to produce higher clamping pressures.
The existing work-holding chassis typically are bulky blocks of steel mounted on a heavy base plate by which the chassis and its cargo of parts is moved from station to station. In some instances, these lines are fully automated with the various operations being programmed into the computer controller. The principal problem with these prior art chassis is their bulk. A secondary problem is their lack of versatility. The bulkiness takes its toll on the equipment being utilized in moving these chassis. In addition, the workmen have to manually index the chassis to load and unload them. This can result in muscle, tendon, and ligament strain in the repetitive moving of the chassis, day in and day out. The lack of versatility adds to the per part cost of manufacture. Since a chassis is constructed for the finishing of a particular type of part, once that part has run its course, the tombstone becomes scrap material. In some instances, the lack of versatility of the work-holding chassis results in its being scrapped for simply a design change in the part or a change in the machining required. A further drawback of existing tombstones is the use of external hydraulic lines. These lines are external to the periphery of the chassis and, are thereby, restrictive to tool-to-the-workpiece approach and are subject to damage which leads to significant down time.
The light-weight, modular work-holding chassis of the present invention overcomes these shortcomings. The work-holding chassis is comprised of at least one lower manifold/bracket having a first geometric shape; at least one upper manifold/bracket having a second identical geometric shape spaced from the lower manifold/bracket by a first distance and defining a first volume, the upper and lower manifold/brackets occupying significantly less than an entirety of the first volume; a plurality of fixture plates attachable to the upper and lower manifold/brackets; means to attach at least one workpiece to the fixture plates. A central manifold/bracket may optionally be positioned intermediate the lower and the upper manifold/brackets to reinforce the plurality of fixture plates. The number of the plurality of fixture plates is preferably equal to the number of a plurality of faces positioned on an external periphery of the first and second geometric shapes.
The means to attach at least one workpiece to the fixture plates includes a plurality of any of various types of clamps for engaging the at least one workpiece. In one application, swing clamps are used with the clamps being hydraulically operated. At least one, and preferably both, of the lower and the upper manifold/brackets contains internal feed lines for hydraulic fluid. In one embodiment, the hydraulic feed lines are completely internal to the manifold/bracket and the fixture plates. Alternatively, each end of these internal feed lines may be equipped with a threaded aperture for receiving couplings from flexible hoses for carrying hydraulic fluid, the flexible hoses being confined within said first volume, i.e., within the boundary of the tombstone.
In another aspect of the invention, a kit for constructing fixtures for mounting workpieces for machining is provided, the kit comprising a first plurality of manifold/brackets having an external periphery with a first geometric shape and a first plurality of sides; a second plurality of manifold/brackets having an external periphery with a second different geometric shape with a second different plurality of sides; a third plurality of fixture plates attachable to both the first plurality of sides and to the second plurality of sides; whereby a workpiece fixture can be formulated with the optimum configuration for a particular application by assembling at least some of the third plurality of fixture plates to one of a group selected from the first plurality of manifold/brackets and the second plurality of manifold/brackets.
Various other features, advantages and characteristics of the present invention will become apparent to one of ordinary skill in the art after a reading of the following specification.